diff -u b/core/includes/form.inc b/core/includes/form.inc
--- b/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -1697,6 +1697,13 @@
     // tableselect element behaves as if it had been of #type checkboxes or
     // radios.
     foreach (element_children($element) as $key) {
+      // Since the #parents of the tableselect form element will equal the
+      // #parents of the row element, prevent FormBuilder from auto-generating
+      // an #id for the row element, so as to prevent drupal_html_id() from
+      // automatically appending a suffix.
+      $element_parents = array_merge($element['#parents'], array($key));
+      $element[$key]['#id'] = drupal_html_id('edit-' . implode('-', $element_parents) . '-row');
+
       // Do not overwrite manually created children.
       if (!isset($element[$key]['select'])) {
         // Determine option label; either an assumed 'title' column, or the
@@ -1734,15 +1741,9 @@
           '#return_value' => $key,
           '#attributes' => $element['#attributes'],
         );
-        $element_parents = array_merge($element['#parents'], array($key));
         if ($element['#multiple']) {
           $element[$key]['select']['#default_value'] = isset($value[$key]) ? $key : NULL;
           $element[$key]['select']['#parents'] = $element_parents;
-          // Since #parents equals the #parents of the row element and
-          // FormBuilder auto-generates an #id for every element, ensure to
-          // suffix the checkbox #id with '-select', so as to prevent
-          // drupal_html_id() from automatically appending a suffix.
-          $element[$key]['select']['#id'] = drupal_html_id('edit-' . implode('-', $element_parents) . '-select');
         }
         else {
           $element[$key]['select']['#default_value'] = ($element['#default_value'] == $key ? $key : NULL);
diff -u b/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestTestForm.php b/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestTestForm.php
--- b/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestTestForm.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestTestForm.php
@@ -147,7 +147,7 @@
       // Cycle through each test within the current group.
       foreach ($tests as $class => $info) {
         $test_id = drupal_clean_id_identifier($class);
-        $test_checkbox_id = 'edit-' . $test_id . '-select';
+        $test_checkbox_id = 'edit-' . $test_id;
         $current_js['testNames'][] = $test_checkbox_id;
 
         $form['tests']['table'][$test_id] = array(